An organic electroluminescence (organic EL) display device is arranged with a light emitting device in each pixel. An organic EL display device displays an image by individually controlling emitted light from the light emitting device. The light emitting device has a structure in which a layer including an organic EL material (organic EL layer) is sandwiched between a pair of electrodes. When a potential is applied to the electrode of the light emitting device, electrons are injected from the cathode and holes are injected from the anode. The electrons and the holes move in the organic layer, recombine with the host molecule of the light emitting layer and release energy. As a result, the luminescent molecules in the light emitting layer are excited by the energy released thereby, and then the luminescent molecules return to the ground state to emit light. The light emission intensity of the light emitting device can be controlled by the applied voltage or the amount of current flowing in the device. Here, in order to obtain higher luminance, a larger voltage may be applied to increase the current density flowing in the light emitting device. However, the increase in current density flowing in the light emitting device results in shortening the lifetime of the light emitting device. Thus, various measures have been taken to obtain high light extraction efficiency.
For example, Japanese Unexamined Patent Application Publication No. 2005-116516 discloses a method of resonating light between a total reflection surface on the anode side and a semi-reflecting surface on the cathode in a top emission type light emitting device to amplify a necessary emission spectrum.
The semi-reflecting surface transmits part of the light emitted by the organic layer, and reflects the other part. The reflected light is transmitted through the organic layer and the anode, and is reflected on the total reflection surface. Subsequently, the reflected light is transmitted through the anode and the organic layer, and part of the light passes through the semi-transparent cathode, and the other part is reflected on the semi-transparent cathode. On the other hand, the total reflection surface reflects the light emitted from the organic layer. The reflected light is transmitted through the anode, the organic layer, and the semi-transparent cathode or is reflected on the semi-transparent cathode. The light generated in the light emitting layer can be converged in the extraction direction, by utilizing the resonance effect of light caused by repeated reflection between the semi-reflecting surface and the total reflection surface.
When the optical resonance structure is applied to the light emitting device, the light emitting position of the organic EL layer between the semi-reflecting surface and the total reflecting surface greatly influences the light extraction efficiency. However, due to restrictions on the film thickness of the organic EL layer, it was almost impossible to freely select the light emitting position.